Question

在下面的查询中，我试图在左外连接中使用第一个表。但是我收到了错误。

SELECT
       products.id,
       products_cstm.oem_c,
       products.mfr_part_num,
       products.description,
       products.cost,
       products.assigned_user_id,
       customfields_oo.ans
FROM products
          LEFT OUTER JOIN (SELECT  COUNT( q.id )  AS ans
                                  , pq.product_id
                           FROM   products_quotes pq 
                                     LEFT JOIN quotes q
                                           ON pq.quote_id = q.id
                           WHERE  q.deleted = 0
                           AND    pq.deleted = 0
                           AND    q.stage <> 4
                           AND  (pq.qty_shipped < pq.product_qty)
                           AND  pq.product_id = products.id
                           GROUP BY pq.product_id
                      ) AS customfields_oo
                ON customfields_oo.product_id = products.id
          LEFT JOIN products_cstm
                ON products.id = products_cstm.id_c
WHERE  products.deleted = 0
ORDER  BY ans DESC

当我运行查询时，它给出了以下错误：

Error Code : 1054
Unknown column 'products.id' in 'where clause'

在左外连接查询中不允许第一个“products”表。

Answer 1

您不需要在where语句中包含AND pq.product_id = products.id。因为你是LEFT JOIN。所以我觉得这样的事情会奏效：

AND (pq.qty_shipped < pq.product_qty)
GROUP BY pq.product_id) AS customfields_oo
ON customfields_oo.product_id = products.id
LEFT JOIN products_cstm
   ON products.id = products_cstm.id_c
WHERE products.deleted = 0
ORDER BY openorder DESC

修改

您LEFT JOIN所在的桌子上不需要COUNT。你也可以这样做：

SELECT ..... ( SELECT COUNT( q.id ) FROM products_quotes pq LEFT JOIN quotes q ON pq.quote_id = q.id WHERE q.deleted = 0 AND pq.deleted = 0 AND q.stage <> 4 AND (pq.qty_shipped < pq.product_qty) AND pq.product_id = products.id ) AS ans FROM products .....

Answer 2

问题是customfields_oo是派生表而不是相关子查询。因此，您无法从派生表的定义中引用外部表。在这种情况下，您无法从products定义中引用外部customfields_oo表。相反，您必须在dervied表定义之外的On子句中执行该过滤。

Select products.id,
       products_cstm.oem_c,
       products.mfr_part_num,
       products.description,
       products.cost,
       products.assigned_user_id,
       customfields_oo.ans
FROM products
    Left Join   (
                Select pq1.product_id
                    , Count( q1.id ) As ans
                From products_quotes As pq1 
                    Left Join quotes As q1
                        On pq1.quote_id = q1.id
                Where q1.deleted = 0
                    And pq1.deleted = 0
                    And q1.stage <> 4
                    And pq1.qty_shipped < pq1.product_qty
                Group By pq1.product_id
                ) As customfields_oo
        On customfields_oo.product_id = products.id
    Left Join products_cstm
        On products.id = products_cstm.id_c
Where products.deleted = 0
Order By customfields_oo.ans Desc

现在，您已经在评论中说明这太慢了，因为产品被删除＆lt;＆gt;可以在派生表中评估0。如果是这种情况，那么只需展开派生表以在外products表上包含过滤器。

Select products.id,
       products_cstm.oem_c,
       products.mfr_part_num,
       products.description,
       products.cost,
       products.assigned_user_id,
       customfields_oo.ans
FROM products
    Left Join   (
                Select pq1.product_id
                    , Count( q1.id ) As ans
                From products_quotes As pq1 
                    Join products As p1
                        On p1.products.id = pq1.product_id
                    Left Join quotes As q1
                        On pq1.quote_id = q1.id
                Where q1.deleted = 0
                    And pq1.deleted = 0
                    And q1.stage <> 4
                    And pq1.qty_shipped < pq1.product_qty
                    And p1.deleted = 0
                Group By pq1.product_id
                ) As customfields_oo
        On customfields_oo.product_id = products.id
    Left Join products_cstm
        On products.id = products_cstm.id_c
Where products.deleted = 0
Order By customfields_oo.ans Desc

如何在LEFT OUTER JOIN中访问外部表

2 个答案: